Petro Poroshenko promised the Ukrainian people he would "bring them peace" after being sworn in as the country's fifth president.

Mr Poroshenko told parliament Ukrainians would "never feel the blessing of peace and security until we resolve our relations with Russia".

He pledged an amnesty to any insurgents in the east who had "no blood on their hands" but said he would not open dialogue with "gangsters and killers".

Ukrainian officials say some 200 people have died during troubles in eastern parts of the country.

Image Caption:Mr Poroshenko arrives for his inauguration

And the 48-year-old tycoon - dubbed the "chocolate king" for his popular brand of sweets - stated he would not accept Russia's seizure of Crimea nor attempts to divert his pro-European course.

"Crimea will remain a part of Ukraine," said Mr Poroshenko.

"Ukraine now returns to its natural European condition that so many generations have longed for."

The inauguration was attended by US Vice President Joe Biden and European Council President Herman Van Rompuy.

The latter sent this message to Russia: "All neighbours ... need to respect (Ukraine's) sovereign choices, including stronger ties with the European Union and its territorial integrity."

Moscow was represented by its acting ambassador to Kiev, Mikhail Zurabov, who said the pledges "sound reassuring".

The Kremlin's only official response to Mr Poroshenko's comments was to call for him to act by "the principles of a democratic society" and release two Russian journalists detained in the east of the country.

Video:Putin And New Ukraine Leader Meet

Meanwhile, Russian president Vladimir Putin reportedly ordered his Federal Security Service to strengthen protection of the country's border with Ukraine to prevent people crossing illegally.

This came after talks with world leaders in France, where US President Barack Obama urged the Kremlin to cease support for separatists in eastern Ukraine - including stopping arms and materials crossing the border.

Insurgents in both Luhansk and Donetsk responded to Mr Poroshenko's pledge of an amnesty with scepticism.